This invention refers to a method and an apparatus for mixing liquid chemical components which are fed under pressure conditions and which are capable of reacting with one another for the manufacture of polyurethane resins, bi-component resins and molded articles; according to the invention positive use is made of the turbulence and the vorticity or swirling induced by the injection, and by the impingement of jets of the chemical components in a mixing chamber, through specific injectors appropriately conformed, to provide a methodology tending to improve the mixing processes as compared to those carried out with conventional injectors.